1. Field of Invention
The present invention relates in general to a control circuit of power converter, and more particularly, to a start-up circuit and method for offline power converter.
2. Description of Related Art
The present invention is a start-up circuit with low standby power loss for power converters. A prior art of “Integrated start-up circuit with reduced power consumption” U.S. Pat. No. 6,906,934 that had been disclosed using the bleeding resistor of the EMI filter to start the power converter for the power saving. However, the bleeding resistor still causes a power loss that can be further reduced, particular for the light-load and no-load conditions. The objective of this invention is to use a start-up resistor to start the power converter, and the start-up resistor will be cut off to save the power loss after the start-up operation. Once the AC input power is removed, the start-up resistor will be switched on and coupled to discharge the EMI filter for the safety.